[MikeK]

OK, I've heard this heat shrink/ cold bend debate about frame straightening too many times. Let's apply a little engineering/ math:

If a 4' long straight edge across the motor mount shows a 1/4" (0.250000") sag, the difference in the top and bottom chord will be 0.00260". I dont know if it will be all stretch in the bottom chord or all compression in the top. Likely some mix of the two, as the same sectional area of the same material makes up both chords.

Applying either straightening method, cold or heat, will cause one chord to compress (shorten) as the other stretches. Cold press will cause the chord acted upon (pushed with the jack) to re-compress while the opposite chord stretches. Heat shrink will cause the chord acted upon to shrink while the opposite chord will stretch. Whether the stretch/compress between the two chords will be 50/50 or 90/10 I don't know, but both chords will be affected by either method.

OK, let's assume the worst: 1) The sag caused only one chord to stretch or compress 0.0026". 2) The method or technique you choose and apply to straighten the frame acts only on the wrong chord. 3) Only one of your two frame rails was bent.
RESULT OF STRAIGHTENING: A frame that has one side 0.0052" longer.

If anybody thinks Henry's frames were accurate within 5 thousanths, think again! There's more slop than that in every bolt hole.